Centrifugal casting



Oct. 24, 1933. jw. .1. BRADDocK QENTRIFUGAL CASTING Filed Sept. 24. 1952l xr, H

- Patented Oct. 24, 1933 1,931,888 l oEN'rmFUGAL CASTING.

William J. Braddock, Wheeling, W. Va., assigner to Wheeling BronzeCasting Company, a corporation of West Virginia Application September24, 1932 Serial No. 634,732

4 Claims.

This invention relates to the centrifugal cast--` ing of tubular membersof relatively great di ameter, and relates particularly to thecentrifugal casting of large diameter bronze bushings.

5 In the centrifugal casting of small diameter bronze bushings butlittle diiculty is encountered in obtaining tubular members having aninterior surface which is substantially free from oxidation and isrelatively smooth. vThe ma- '10 chining necessary to give the tubularmember a smooth, finished, interior surface is therefore '20 smoothinterior surface. By the term large diameter tubular castings, orbushings, I wish to include all such castingsv having an interiordiameter greater than five inches. .This is for the reason that above afiveinch interior diameter the centrifugated bronze castingsA tend tohave a rough, and oxidized, interior, and that this undesirable tendencyis increased in castings of increased' diameter.

I n the larger diameter centrifugal castings, for example,.those havingan interior diameter of eight inches and more, the scaling and crack-ging frequently extends from the interior surface such a distance intothe bodyof the casting that a relatively great proportion of the .metalof the casting must be machined off in order to obtain a sound body, anda true and smooth in'- terior surface. i

Variousattempts to prevent oxidation of the metal during the progress ofthe centrifugal cast- 40 ing operation have proven inadequate. Asexamples of such unsuccessful practice, molten glass, welding flux, andcore sand have been introduced into the interior of the tubular memberin the casting machine, on the theory that they would serve as aprotective coating for the interior surface of the tube.

The object of my invention is to so act upon the interior surface ofmolten metal, primarily non-ferrous metal, assuming tubular form in a 50centrifugal casting machine, that the metal adjacent the'interiorsurface is smoothed and oxidation is prevented.

A more general object of my invention is to so act upon material,assuming the form of a hollow cylinder by centrifugal casting, that afinished tubular member ,having a relatively smooth interior surface isproduced.

The accompanying drawing illustrates, in. generalized form, exemplaryapparatus for conducting the Amethod of my invention. In the exem- .60plary drawing, Figure I is a View showing a centrifugal casting machineand mold in vertical section, andl showing in side elevation means foracting upon the .interior surface of the casting during the progress ofthe centrifugal casting 55 operation; Figure II is a cross-sectionalview through the casting machine and apparatus, taken on the line II-IIof Figure I; Figure III' is a fragmentary view, in vertical section,taken on the line III-IIIof Figure I, showing a suita- 0 ble form ofsupport for smoothing means used in conducting the method of myinvention with tools of simple form; Figure IV is a side elevationillustrating, as an example, .mechanism suitable for conducting themethod of myinvention; and Figure V, taken on the line V-V of Figure IV,shows in cross-section and on a greatly en larged scale a shoe suitablefor use in conducting my method.

In conducting a method of centrifugally casting large diameter bronzebushings, in' accordance with my procedure, a casting machine 1,containing a liner or mold 2, is causedto revolve rapidly about itsaxis. The bronze, in liquid condition, is introduced by means of aremovable pouring basin, and the basin is removed from before the openend of the casting machine.

Immediately upon` removal of the pouring basin, supports 3 for thesmoothing tools may be brought into position before the open end of thecasting machine. .As shown in Figure I of the drawing, these smoothingtools comprise a rod 4, carrying a lsmoothing shoe.5, and a tube' 6 forconveying water, or other suitable fluid to the smoothing shoe.

The operator, by moving shoe 5 backwardly and forwardly, causes it totraverse the interior surface of the casting longitudinally. As thecasting machine is simultaneously revolving about its axis at relativelyhigh speed, the shoe is thus repeatedly brought to bear upon the entireinterior surface of the casting. In addition to traversing the smoothingshoe over the interior surface of the casting, the operator causes it tobear down upon the molten metal, so that it exerts a compacting effecton the metal adjacent the lnterior surface.

It will be noted, particularly by reference to Figures Il and V of thedrawing, that the metalcontacting face of smoothing shoe 5 is desirablyformed on an irregular curve, with the'trailing portion of the faceformed on a radius less than thatupon which the edge portion ,presentedto the rotating movement of the machine and` mold is formed. The shoealso has its greater Weight to the "trailing side of the mounting,sothat its inherent tendency is to rotate counter to the direction ofrotation of the machine and the casting. This conformation tends toprevent the shoe from ploughing deeply into the metal at the beginningof the operation, when the metal is in its condition of higherliquidity.

It is possible that the smoothing shoe may be made of various materials.The material which I have found most satisfactory for the shoe is hardWood. Since, during the casting operation,V

the shoe 5, may be sprayed with a cooling liquid from pipe 6, thesurface of the shoe which is presented to the molten metal chars slowlyunder the conditions of the process. This slow charring of the shoepossesses positively advantageous features. Thus, the charring causesthe metal-contacting region on the operating face of the shoe to Wearaway to such extent as to assume approximately the radius of curvatureof the casting bore. This effect avoids the necessity of using a numberof Ashoes of varied curvature, predetermined with reference to thediameter of the various castings with which they are used. The slowcharring also gives the operating surface of the shoe the qualities ofan instrument for fine smoothing.

In practice I have found that a metal shoe, as for example a shoe madeof iron, may be used. An iron shoe, however, does not conform thecontacting region of its operating surface to the bore curvature of thecasting by charring. There is also a tendency, present at the beginningof the process, for an iron shoe to stick to, and pick up, the metal ofthe casting. If a wooden shoe be used during the initial stages of theoperation, a metal shoe, having its operating surface appropriatelycurved, may be used with satisfaction during the concluding stages ofthe operation.

It is probable that bre composition shoes, having the sloW-charringproperty of hard wood, may prove wholly as satisfactory in service asthose made of wood.

In addition to its function of preventing combustion of a combustibleshoe, and regulating the rate of charring on the operating face of theshoe, the spray of cooling liquid performs the additional function ofchilling the metal of the casting, and expediting its congelation.

As a variation of my method, I may use a shoe extending the entirelength of the casting, and bring pressure to bear on it. For somereason, or reasons, this practice is less satisfactory than the use of asmaller shoe moved forwardly and backwardly in the casting. It does,however, to an appreciable extent, improve the interior surface of acentrifugal casting in comparison with an operation in which nosmoothing pressure is exerted on the interior surface of the casting.

Figure IV of the drawing shows an alternative, exemplary, mounting forthe smoothing tool and spray tube. In this arrangement the spray tube 7serves also as a mounting rod for the shoe 5, and the shoe is so mountedthereon as to provide a channel or ,channels for the passage of coolingliquid to and along the surface of the shoe'. The tube 7 is mounted fordirect hand reciprocation in holders 8, carried by threaded stems 9.Stems 9 may be caused to rotate by means of worms 10,

carried by a rotatable lay shaft 12 and co-operating with gears 11 onthe stems.

In use of this arrangement, the tubular shoecarrying rod 7 isreciprocated directly by hand, and the shoe is caused to bear down onthe casting by rotating lay shaft 12. v

Various other mechanical installations, more or less automatic in theirnature may be employed. By use of the device shown in FigureIV, however,I have found that any mechanical means are less desirable, at thebeginning of the casting operation, than a simple hand operation, suchas that indicated in Figures I and II. This is for the reason that asimple hand operation permits the operator to get the feel of the work.The operator having this feel may avoid the exertion of too greatpressure on the casting while the metal is in its initial condition ofhigher.

interior, or bore, surface of the casting.

I claim as my invention: A 1. In the art of centrifugal casting, thehere described method of obtaininga sound body adjacent the bore of atubular member of nonferrous metal and a true and relatively smooth boresurface of the tubular member, which comprises traversing throu'ghodtthe greater proportion of the casting operation a smoothing toolcooperatively curved with respect to the bore curva ture ofthe tubularmember i'n process of forma.- tion and having the approximate qualitiesof hard Wood longitudinally of the interior surface of the fluid metalcentrifugated to form the tubular member, exerting pressure on the boresurface by means of said smoothing tool as it is traversed, and exertingon the smoothing tool in its use a cooling effect to retard `combustionof the smoothing tool.

l2. In the art of centrifugal casting, the herein described method ofobtaining a sound body adjacent the bore of a tubular member ofnonferrous metal and a true and relatively smooth bore surface of thetubular member, which comprises traversing. throughout the greaterproportion of the casting operation a smoothing tool co-operativelycurved with respect to the bore curvature of thetubular-member inprocess of formation and having the approximate qualities vof hard woodlongitudinally of the interior surface of the fluid metal 'centrifugatedto form the For example, it has been found valuable4 traversed, andsupplying acooling liquid tothe surface of the smoothing tool.

3. In the art of centrifugal casting, the herein described method ofobtaining a sound body adjacent the bore of a tubular member of nontoform the tubular member, exerting pressure on the bore surface by meansof the smoothing tool as it is traversed, and supplying a cooling liquidmember in process of formation and controllably combustible under thetemperature conditions of the process longitudinally of the interiorsurface of the uid metal centrifugated to form the tubular member,exerting pressure on the bore surface by means of said smoothing tool asit is traversed,

4and controlling combustion of the smoothing tool by exerting a. coolingeiect on the smoothing tool in its use.

WILLIAM J. BRADDOCK.

